The button for facebook sharing has been removed some 2 years ago, because Facebook has stopped supporting it for dynamically created content. In turtle you can choose the "Separate slides mode" which puts every slide image on a separate HTML page (Settings / Pages / Make slides). Please note this mode has several drawbacks: no background music, no smooth transitions, etc., see here: https://jalbum.net/en/blog/entry/dynamic-vs-separate-slides-mode-in-turtle-skin